Lake Tahoe SHOALS Data

Frequently-anticipated questions:

• What does this data set describe?
  1. How should this data set be cited?
  2. What geographic area does the data set cover?
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
  5. What is the general form of this data set?
  6. How does the data set represent geographic features?
  7. How does the data set describe geographic features?
• Who produced the data set?
  1. Who are the originators of the data set?
  2. Who also contributed to the data set?
  3. To whom should users address questions about the data?
• Why was the data set created?
• How was the data set created?
  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
  3. What similar or related data should the user be aware of?
• How reliable are the data; what problems remain in the data set?
  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
  4. Where are the gaps in the data? What is missing?
  5. How consistent are the relationships among the data, including topology?
• How can someone get a copy of the data set?
  1. Are there legal restrictions on access or use of the data?
  2. Who distributes the data?
  3. What's the catalog number I need to order this data set?
  4. What legal disclaimers am I supposed to read?
  5. How can I download or order the data?
• Who wrote the metadata?

Title: Lake Tahoe SHOALS Data

Abstract:

These data were collected by the SHOALS (Scanning Hydrographic Operational Airborne Lidar Survey) system which consists of an airborne laser transmitter/receiver capable of measuring 400 soundings per second.

Supplemental_Information:

The system operates from a deHavilland DHC-6 Twin Otter flying at altitudes between 200 and 400 meters with a ground speed of about 100 knots. The SHOALS system also includes a ground-based data processing system for calculating acurate horizontal position and water depth. Lidar is an acronym for LIght Detection And Ranging. The system operates by emitting a pulse of light that travels from an airborne platform to the water surface where a small portion of the laser energy is backscattered to the airborne receiver. The remaining energy at the water's surface propogates through the water column and reflects off the sea bottom and back to the airborne detector. The time difference between the surface return and the bottom return corresponds to water depth. The maximum depth the system is able to sense is related to the complex interaction of radiance of bottom material, incident sun angle and intensity, and the type and quantity of organics or sediments in the water column. As a rule-of-thumb, the SHOALS system should be capable of sensing bottom to depths equal to two or three times the Secchi depth.

1. How should this data set be cited?

   US Army Engineer Joint Airborne Lidar Bathymetry Technical Center of Expertise.(ed.), 20011101, Lake Tahoe SHOALS Data.

2. What geographic area does the data set cover?

   West_Bounding_Coordinate: -120.162778

   East_Bounding_Coordinate: -119.932500

   North_Bounding_Coordinate: +39.260278

   South_Bounding_Coordinate: +38.930278

3. What does it look like?

4. Does the data set describe conditions during a particular time period?

   Calendar_Date: Jul-2000

   Currentness_Reference: Ground Condition

5. What is the general form of this data set?

   Geospatial_Data_Presentation_Form: ArcInfo export

6. How does the data set represent geographic features?
   1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: Lake Tahoe

   2. What coordinate system is used to represent geographic features?

      Grid_Coordinate_System_Name: Universal Transverse Mercator

      Universal_Transverse_Mercator:

      UTM_Zone_Number: 10

      Transverse_Mercator:

      Scale_Factor_at_Central_Meridian: 0.9996

      Longitude_of_Central_Meridian: -123.00000

      Latitude_of_Projection_Origin: 0.00000

      False_Easting: 0.00

      False_Northing: 0.00

      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 10.0
      Ordinates (y-coordinates) are specified to the nearest 10.0
      Planar coordinates are specified in Meters

      The horizontal datum used is WGS84.
      The ellipsoid used is WGS84.
      The semi-major axis of the ellipsoid used is 6378137.00 meters.
      The flattening of the ellipsoid used is 1/0.003352811.
      

7. How does the data set describe geographic features?

1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
   • US Army Engineer Joint Airborne Lidar Bathymetry Technical Center of Expertise.(ed.)

2. Who also contributed to the data set?

3. To whom should users address questions about the data?

   U.S. Army Corps of Engineers JALBCTX
   109 St. Joseph Street
   Mobile, Alabama 36602
   

   334-690-3467 (voice)
   334-690-3464 (FAX)
   

The purpose of the Lake Tahoe survey was to collect bathymetry data from the shoreline to -10 meter depths.

1. From what previous works were the data drawn?

   None (source 1 of 1)

   U.S. Army Corps of Engineers JALBTCX, 20001200, Lake Tahoe.

   Type_of_Source_Media: CD-ROM

   Source_Contribution: SHOALS

2. How were the data generated, processed, and modified?

   Date: 2000 (process 1 of 1)

   The SHOALS airborne system acquires a tremendous volume of raw data during a single mission. The lidar data are unique and require a specialized Data Processing System (DPS) for post-processing. The DPS main funcions 1) import airborne data stored on high density data tape; 2) perform quality control checks on initial depths and horizontal positions; 3) provide display and edit capabilities; 4) calculate depth and position (XYZ) values for each sounding; and 5) output final positions and depths for each sounding.

3. What similar or related data should the user be aware of?

1. How well have the observations been checked?

   SHOALS has demonstrated capabilities that meet US Army Corps of Engineers Hydrographic Survey accuracy requirements for Class 1 surveys and the International Hydrographic Organization nautical charting standards for Order 1.

2. How accurate are the geographic locations?

   +/- 3 meters (1 sigma)

3. How accurate are the heights or depths?

   +/- 15 cm (1 sigma)

4. Where are the gaps in the data? What is missing?

   Complete

5. How consistent are the relationships among the observations, including topology?

   None

Are there legal restrictions on access or use of the data?

Access_Constraints: None

Use_Constraints:

Acknowledgement of the U.S. Army Engineer Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBCTX) would be appreciated in products derived from these data.

1. Who distributes the data set? (Distributor 1 of 1)

   USACE, SACRAMENT DISTRICT
   c/o Phillip Brozek
   
   CESPK-PM-C
   
   1325 J STREET
   
   SACRAMENTO, CA 95819-2922
   

   916-557-7630 (voice)
   

2. What's the catalog number I need to order this data set?

3. What legal disclaimers am I supposed to read?

   None

4. How can I download or order the data?

Dates:

Last modified: Dec-2000
Last Reviewed: Feb-2000

Metadata author:

USACE, SACRAMENTO DISTRICT
c/o Phillip Brozek

CESPK-PM-C
1325 J STREET

SACRAMENTO, CA 95819-2922

916-557-7630 (voice)

Metadata standard:

Content Standard for Digital Geospatial Metadata ("CSDGM version 2") (FGDC-STD-001-1998)